1. Field of the Invention
The present invention relates to a method of improving the light fastness of color images formed in a color diffusion transfer photographic system.
2. Description of the Prior Art
Various types of anti-fading agents have been known for improving the light fastness of color images in the color diffusion transfer photographic system. However, they are not always completely effective. For example, a light reflecting layer containing tert-butyl hydroxyanisole has been disclosed in Research Disclosure, No. 15162, p. 82, but its ability to prevent light fading is not sufficient and it discolors into a yellowish brown color and contaminates the light reflecting layer when it is exposed to light for long periods of time.
It has been disclosed in U.S. Pat. No. 3,700,455 that light fading in general color photographs can be prevented by the presence of bisphenol derivatives with dyes forming the color images. It is also disclosed in that same U.S. Patent that the light fastness of color images is improved using bisphenol derivatives in the image-receiving layer used in conjunction with color diffusion transfer process. However, in the case of a color diffusion transfer process using a light reflecting layer which is laminated as shown in Belgian Pat. Nos. 757,960 and 757,959, the effect of preventing light fading of color images is insufficient if the anti-fading agent is added to the image-receiving layer (hereafter the mordant layer).
In the case of the above-described color diffusion transfer process using a light reflecting layer, it has been found that excellent light fastness can be obtained by adding a certain class of compound to the light reflecting layer as opposed to adding it to the mordant layer. This is truly an unexpected result.